Rats were fed by stomach tube with 50 mg/kg B.W./day capsaicin (Sigma) or 0.5 gm/kg B.W./day capsicum fruit crude extract for 60 days. The influences of capsaicin or capsicum upon body weight, rectal temperature, food and water consumptions, haematological parameters, plasma chemistry, urine concentration and dilution tests, together with the relative organ weight, were evaluated at 10, 20, 30, 40, 50 and 60 days. The results showed that there were significant reductions of the growth rate in both capsaicin and capsicum treated groups. However, the food intake in both experimental groups increased steadily throughout the experimental periods. There were no significant differences from the control rats in the rectal temperature, water intake, plasma chemistry, urine dilution and concentration, and the relative organ weights. After one month of oral administration of capsaicin or capsicum, there were significant reductions of plasma urea nitrogen, glucose, phospholipids, triglycerides, total cholesterol, free fatty acids, glutamic pyruvic transaminase, and alkaline phosphatase. It is also interesting to observe that capsicum fruit crude extract exerted more influences on the various biological parameters being studied here than its pungent substance, capsaicin. Therefore, it is concluded that capsaicin or capsicum, if given orally for a relatively longer period, may have a mild effect on the experimental animals.